1. Field of the Invention
The present invention relates to a styrene polymer composition. More particularly, it is concerned with a styrene polymer composition which is suitable to be molded into industrial materials such as electric and electronic materials (e.g., connector, and printed substrates), construction materials for industrial use, parts of automobiles (e.g., connectors for the use in vehicles, wheel caps, cylinder head cover, etc.), parts of home electric appliances, and various machines.
2. Description of the Related Arts
Heretofore, synthetic resins have been improved in their mechanical properties, particularly, rigidity and heat resistance, by compounding inorganic fillers including glass fiber with them. Styrene polymers, however, have not a sufficient adhesivity to inorganic fillers so that additives to improve their adhesivity and surface-treating agents of inorganic fillers have been studies. As the result, various surface-treating agents which contain various kinds of aminosilane compounds with polyester type resins, or vinyl acetate type resins, and also additives such as maleic anhydride/styrene copolymers and the like have been developed. Specifically, surface-treating agents such as silane-based coupling agents for glass fibers and the like, and a composition containing an additive, such as a styrene/maleic anhydride-styrene/glass fiber composition (Japanese Patent Application Laid-Open No. 161836/1980, Japanese Patent Application Laid-Open No. 19097/1970) have been known. However, these had not sufficiently improved effects yet.
Japanese patent Application Laid-Open No. 257948/1987 and other proposed resin compositions which were excellent in heat resistance and mechanical properties, and which were obtained by adding an inorganic filler to a styrene polymer having a syndiotactic configuration, or adding a thermoplastic resin and/or a rubber and an inorganic filler to a styrene polymer having a syndiotactic configuration. Also in these compositions, however, the adhesivity between the styrene polymer having a syndiotactic configuration and the inorganic filler was insufficient, and had room for improvement.
To be more specifically, when the conventional inorganic fillers surface-treated with various surface-treating agents, and additives were added to the styrene polymer, the adhesivity with styrene polymer, especially a polystyrene having a syndiotactic configuration was insufficient, and the resulting compositions were poor in impact resistance, and none of them had a Izod impact strength (notched) of more than 6.0 kg cm/cm. Accordingly, a styrene polymer composition having an improved impact resistance has been desired.
On the other hand, polyamides have been used as the material to be molded into various products such as domestic products, electric products and parts of machines or devices, since they are excellent in moldability and heat-resistance, and have a sufficient rigidity.
In spite of these excellent properties, however, polyamide has a disadvantage in that it is far from being sufficient in water resistance.
The group of the present inventor has attempted to remove the above disadvantage by blending, with polyamide, a styrene polymer having a high degree of syndiotacticity, but the effect of improving the properties by blending met a limitation, for the composition of such resins as polyamide and polystyrene that are substantially incompatible with each other could not avoid a fall in mechanical properties due to the insufficient strength of the interface between the phases.
Under the circumstances, the present inventor has repeated earnest studies to develop a styrene polymer composition excellent in all of impact resistance, heat resistance, and mechanical strength which has never seen before. Further, the study has proceeded, also in order to develop a composition greatly improved in heat resistance and water resistance, without lowering the mechanical properties of polyamide, by improving the compatibility between a styrene polymer having a syndiotactic configuration and a polyamide resin.